A person of mass stands on a frictionless skateboard holding a box

PHYSICS · Single correct · CBSE · Physics · Laws of Motion · Laws of Motion

Problem

A person of mass 70 kg70\,\text{kg} stands on a frictionless skateboard holding a 10 kg10\,\text{kg} box. The system is initially at rest relative to the ground. The person throws the box horizontally so that the box moves away at 5 m s−15\,\text{m}\,\text{s}^{-1} relative to the ground. During the 2.0 s2.0\,\text{s} it takes to complete the throw, a steady horizontal wind exerts a 4.0 N4.0\,\text{N} force on the person–skateboard combination in the same direction the box is thrown. What is the person’s speed relative to the ground at the end of the 2.0 s2.0\,\text{s} interval? (a) 0.71 m s−10.71\,\text{m}\,\text{s}^{-1} opposite to the box’s motion (b) 0.11 m s−10.11\,\text{m}\,\text{s}^{-1} in the same direction as the box’s motion (c) 0.60 m s−10.60\,\text{m}\,\text{s}^{-1} opposite to the box’s motion (d) 0.60 m s−10.60\,\text{m}\,\text{s}^{-1} in the same direction as the box’s motion

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